JP2018518137A - Hollow shaft arrangement - Google Patents

Abstract

The present invention relates to a hollow shaft (2), in particular a hollow shaft arrangement (1) comprising a rotor shaft of an electric motor, through which fluid can be passed for cooling, and the hollow shaft (2) A surface expansion cooling structure (9) for transferring heat energy from the hollow shaft (2) to the fluid is disposed in the internal space (3). The cooling structure (9) is connected to the hollow shaft (2), and the cooling structure (9) is a part of the cooling body (8) formed separately from the hollow shaft (2).
[Selection] Figure 1

Description

  The invention relates to a hollow shaft arrangement according to the preamble of claim 1 and a method for assembling the hollow shaft arrangement according to claim 11.

  DE 102008043367 A1 discloses a hybrid drive device for a motor vehicle having an internal combustion engine and an electric motor and in each case for driving the motor vehicle. The rotor of the electric motor is disposed on the hollow shaft of the drive train. Means for conveying the cooling fluid conveys the cooling fluid through the interior space of the hollow shaft to cool the rotor and the hollow shaft.

  In order to transfer heat to the cooling fluid in the best possible way, cooling fins are arranged in the interior space of the hollow shaft. The cooling fins are integrally formed on the inner wall of the hollow shaft in a rather complicated way. Furthermore, the inner diameter of the hollow shaft, and hence the diameter of the area available for cooling, is very small, resulting in limited cooling performance.

German Patent No. 102008043367A1

  The object of the present invention is therefore to provide a hollow shaft arrangement which is characterized in particular by a simple structure, very good cooling behavior and easy assembly.

  The object is achieved in conjunction with characteristic features due to the hollow shaft arrangement as in the preamble of claim 1. Advantageous refinements of the invention are specified in the dependent claims and the description.

  According to the present invention, there is provided a hollow shaft arrangement, particularly for a hybrid vehicle drive train, comprising a hollow shaft, in particular a rotor shaft of an electric motor, through which fluid can pass for cooling purposes. Is done. A surface expansion cooling structure for transferring thermal energy from the hollow shaft to the fluid, in particular cooling fins, is arranged in the internal space of the hollow shaft. The cooling structure is connected to the hollow shaft. The hollow shaft arrangement is characterized in that the cooling structure is part of a cooling body that is formed separately from the hollow shaft.

  Therefore, the cooling body is manufactured separately from the hollow shaft. In this case, a material having high thermal conductivity but not affected by high demands on strength is suitable for manufacturing a cooling body. In particular, aluminum-based alloys have proven advantageous. Since a complicated cooling structure is not formed inside the relatively long hollow shaft, the hollow shaft itself can be easily manufactured.

  The cooling body is advantageously held in a press-fit manner in the interior space. In particular, the cooling body is clamped in the radial direction within the internal space. Advantageously, no additional radial fastening is provided, so that the cooling body is held in the interior space only by a radially acting press-fit connection. For this purpose, a radially compressible cooling body is used, in particular in an unstressed state, having an outer diameter larger than the inner diameter of the hollow shaft into which the cooling body is inserted. For assembly, the cooling body is radially compressible so that the outer diameter is smaller than the inner diameter of the hollow shaft, i.e. the outer diameter of the cooling body depends on the radial mechanical load and in particular prestressing. Can be reduced during the process of receiving. The cooling body is then inserted into the hollow shaft and subsequently the radial load is removed, whereby the cooling body re-expands, in particular in this case elastically rebounding and press-fits into the inner wall of the hollow shaft. In contrast, it is supported radially.

  The outer diameter of the cooling body is advantageously larger than the inner diameter of the bearing for mounting the hollow shaft, in particular two bearings. As a result, a large cooling body and a large contact surface between the cooling body and the hollow shaft allows a good cooling capacity and at the same time for mounting a hollow shaft that is small in the radial direction and thus low in cost and weight. A bearing is used, which is further characterized by a relatively low friction loss during operation.

  The outer peripheral surface of the cooling body is advantageously formed so as to complement the inner peripheral surface of the hollow shaft, and in particular, the outer peripheral surface and the inner peripheral surface are formed in a cylindrical shape with an outer diameter and an inner diameter corresponding to each other. Has been. “Outer diameter and inner diameter corresponding to each other” means in particular the diameter in the assembled state of the arrangement. As a result of the complementary configuration, a large contact surface is provided between the hollow shaft and the cooling body, thereby promoting good heat transfer capability. Furthermore, a hollow shaft having a cylindrical inner surface can be easily manufactured.

  The cooling body advantageously includes a sleeve-like body from which the cooling structure projects radially inward. The sleeve-like body in particular provides a cylindrical surface that serves to abut the hollow shaft. In particular, including the corresponding dimensions, the sleeve-like form provides the elasticity required for radial compressibility.

  The sleeve-like body advantageously obtains radial compressibility in that the body has a circumferential region that can be reduced in the circumferential direction. Said circumferential region is formed in particular by an axial gap. In the circumferential region, the outer periphery of the sleeve-like body, and thus the outer diameter, can be reduced without plastic deformation. Furthermore, the circumferential region always has an optimum abutment between the cooling body and the hollow shaft, both at low and high temperatures, despite the different coefficients of thermal expansion of the hollow shaft and cooling body materials. Make it possible. Said shrinkable circumferential region, in particular an axial gap, advantageously extends over the entire axial length of the body.

  As an advantageous improvement, the two ends of the sleeve-like body separated from each other by the circumferential region are connected to each other via an expansion fold projecting radially inward. Even in the case of a relatively small reduction around the sleeve-like body, the expansion fold is subjected to a relatively large deformation, so that a high prestress can be achieved. The deformability parameter, and hence the amount of prestress, can be set by dimensioning the expansion fold.

  The hollow shaft is advantageously in the form of a plurality of parts, comprising at least one, in particular a sleeve-like receptacle part, with an axial opening for inserting the cooling body before final assembly, At least one closing portion for closing the axial opening is provided. The receptacle part and the closure part are fixedly connected to each other during assembly, for example by an interference fit. However, prior to this, the cooling body is inserted through the opening into the interior space of the hollow shaft. The hollow shaft is then closed by the closing part. The closing part is in particular formed, for example, as a flange formed integrally with the joinable shaft part.

  The invention further relates to a method for assembling a hollow shaft arrangement of the type described above, which method reduces the radial dimension of the cooling body by means of the following method steps, the load of forces acting radially inward, in particular: A step of elastically reducing, a step of inserting a radially reduced cooling body through the axial opening into the interior space, and removing a radial load so that the cooling body is In particular elastically increasing in a radial direction and receiving a press-fit connection to the hollow shaft. The installed cooling body advantageously has an outer diameter that is reduced by at least 0.5% compared to the non-installed cooling body, so that there is a gap between the hollow shaft and the cooling body over a large temperature range. Resulting in the radial prestress required for the press-fit connection of See the identified advantages with regard to the device and further configurability. Due to the elastic shape change behavior, in particular perfect contact between the hollow shaft and the cooling body and thus a high heat transfer capacity is ensured over different operating temperatures.

  Additional means for improving the invention are presented in more detail below, together with a description of advantageous exemplary embodiments of the invention based on the following drawings.

1 is a longitudinal sectional view of a hollow shaft arrangement according to the present invention. 2 includes a front view of the cooling body with the hollow shaft arrangement of FIG. 1 and FIG. 2b, which is a perspective view of the cooling body with the hollow shaft arrangement of FIG. 3 includes a front view showing an improvement of the cooling body with the hollow shaft arrangement of FIG. 1 and FIG. 3b showing a perspective view of the improvement of the cooling body with the hollow shaft arrangement of FIG. .

  FIG. 1 shows a hollow shaft arrangement 1 according to the invention, which can be used, for example, in a drive train of a hybrid vehicle. The hollow shaft arrangement 1 comprises a rotor shaft 2 in the form of a hollow shaft. On the outer periphery of the rotor shaft 2, a rotor of an electric motor is fastened. The rotor stack 4 can be seen. At one axial end of the rotor shaft 2, the shaft comprises a first shaft portion 16, so that the internal combustion engine can be connected to the first shaft portion 16. A fan wheel 19 is disposed between the internal combustion engine and the rotor shaft 2, and the cooling fluid is conveyed into the internal space 3 of the hollow shaft via the fan wheel 19. At the other axial end of the rotor shaft 2, the shaft comprises a second shaft part 17 including an inner tooth part 20, and a shift gear box (not shown) connected to the drive shaft is connected to the second shaft part. 17 can be connected. The rotor shaft 2 is attached to a vehicle body or a vehicle frame via two rolling bearings 13. A bearing seat 14 for the rolling bearing 13 is provided on the two shaft parts 16, 17 in each case.

  The rotor shaft 2 has a plurality of portions, and includes a separate receptacle portion 5 in an axial central region. The receptacle portion 5 has a sleeve-like shape and has both a cylindrical outer surface and a cylindrical inner surface 12. The sleeve-like receptacle part 5 defines a radially inner space 3 in which a cooling body 8 presented in more detail on the basis of FIGS. 2 and 3 is arranged. At both axial ends, the sleeve-like receptacle part 5 comprises an opening 15 that is closed in each case by the first closing part 6 or the second closing part 7. A first shaft portion 16 and a second shaft portion 17 are integrally joined to the first closing portion 6 and the second closing portion 7, respectively.

Thus, the rotor shaft 2 is formed from a first shaft portion 16, a first closing portion 6, a receptacle portion 5, a second closing portion 7 and a second shaft portion 17. The two closing parts 6, 7 are each fixedly connected to the receptacle part 5, for example by an interference fit or a weld seam. It can be seen that in the assembled state, the outer diameter D ₈ of the cooling body 8 and the inner diameter d ₁₂ of the cylindrical inner surface 12 are considerably larger than the inner diameter d ₁₃ of the two rolling bearings 13. Thus, in the case of the rotor shaft 2 according to the invention, it is possible to provide a small rolling bearing, but it is still possible to use a cooling body 8 having a relatively large diameter. To date, these two characteristics have been incompatible.

  2a and 2b show the cooling body 8 in detail. The cooling body 8 includes a sleeve-like body 18 from which a large number of cooling fins 9 protrude radially inward. The outer peripheral surface 10 of the sleeve-shaped main body 18 has a substantially cylindrical shape. The sleeve-like body 18 has an axial gap 11 extending over the entire length in the axial direction, whereby the body 18 is in principle elastically compressible in the radial direction. Due to the compression in the radial direction, the cooling body 8 can be prestressed in the radial direction. The body 18 can automatically expand from this compressed state as soon as there is no load generating compression. As a result of the axial gap 11, two exposed ends 21 of the body 18 are formed when viewed in the circumferential direction U.

Radial compressibility is exploited during assembly of the arrangement. The cooling body 8 has an outer diameter D ₈ that is initially larger than the inner diameter d ₁₂ of the inner surface 12 of the receptacle portion 5 when not assembled. For assembly, the cooling body 8 is compressed radially by a radial load and is thus prestressed. In this case, the outside diameter D ₈ of the cooling body 8, the outer diameter is reduced so elastically smaller than the inner diameter d ₁₂ of the inner surface 12. In this state, the cooling body 8 is inserted into the internal space 3 through the one axial opening 15. The radial load is then removed and the cooling body springs back elastically. In this case, the cooling body 18 expands in the radial direction and tries to return to its starting state. In a state where the unstressed, since the inner diameter d ₁₂ of the receptacle portion 5 is smaller than the outer diameter D ₈ of the cooling body 8, pressed from the inside in the radial direction against the inner surface 12 at the time the cooling body 8 receptacle portion 5 Thereby, it is fastened to the receptacle part 5 by press fitting. Further radial fastening is no longer necessary. However, as can be seen from FIG. 1, the positioning of the axial form fitting of the cooling body 8 in the internal space 3 can be carried out by two closing parts.

Outer diameter D ₈ of the non-installation state, than the radial installation space which is expected is defined by the inner diameter d _12, of at least 0.5%, especially at most 2.5% greater than the cooling body 8 is particularly suitable. The compressibility of the cooling body can be improved by increasing the circumferential axial gap, but this reduces the outer surface of the cooling body and reduces contact with the hollow shaft, thereby reducing the cooling body This leads to a decrease in the heat transfer capacity. It is therefore preferable to limit the axial gap and thus the compressibility to the absolutely necessary degree.

  In a particularly suitable material pair, the receptacle part 5 is a steel part and the cooling body 8 is an aluminum part.

For a typical outer diameter D ₈ of about 80 mm, the axial gap 11 comprises a gap width B of 0.5 mm to 10 mm, and advantageously comprises a gap width B of about 1.2 mm at 20 ° C. installation. .

In the configuration according to the present invention, the size of the cooling body 8 is independent of the bearing inner diameter d ₁₃ of the rolling bearing 13. Accordingly, the bearing inner diameter d ₁₃ can be chosen to be very small, at the same time, the cooling body 8 can be designed in accordance with the heat transfer capability required independently of it. Since the cylindrical contact surface between the inner surface 12 of the receptacle part 5 and the cooling body 8 is large, there is a large contact surface for heat transfer, and the cylindrical inner surface 12 of the receptacle part 5 and the cylindrical outer surface of the cooling body 8. Full surface contact with 10 is ensured by elastic prestress over a large temperature range.

  FIG. 3 shows an improvement of the cooling body according to FIG. Two ends 21 of the sleeve-like body 18 separated from each other by the axial gap 11 are connected to each other via an extended folding part 22 protruding radially inward. In the case of the present invention, the extended folding part is U-shaped. The design of the extended fold has a considerable effect on the elastic parameters of the sleeve-like body. The elasticity of the extension fold, and thus the elasticity of the body, can be set by the wall thickness, size and shape of the extension fold 22.

  The invention is not limited to the exemplary embodiments described above with respect to that embodiment. Rather, many variations utilizing the presented solution are possible, even in radically different embodiments. All features and / or advantages arising from the claims, description or drawings, including structural details or spatial arrangements, are essential to the invention both individually and in a very wide variety of combinations. Can do.

DESCRIPTION OF SYMBOLS 1 Hollow shaft arrangement | positioning 2 Hollow shaft / rotor shaft 3 Inner space 4 Stacked pack 5 of electric motor rotor Receptacle part 6 First closing part 7 Second closing part 8 Cooling body 9 Cooling fin 10 Cylindrical outer surface 11 of cooling body Axial air gap 12 Cylindrical inner surface 13 of receptacle portion Rolling bearing 14 Bearing seat 15 Opening portion 16 in central portion First shaft portion 17 Second shaft portion 18 Sleeve-like body 19 Fan wheel 20 Inner tooth portion 21 Sleeve-like body End 22 Expanded folding part D8 Outer diameter d12 of cooling body Inner diameter d13 of cylindrical inner surface of receptacle part Inner diameter B of rolling bearing Gap width U Circumferential direction

Claims (12)

A hollow shaft (2), in particular a rotor shaft of an electric motor, through which the fluid can pass for cooling purposes,
A surface expansion cooling structure (9) for transferring thermal energy from the hollow shaft (2) to the fluid is disposed inside the internal space (3) of the hollow shaft (2),
Hollow shaft arrangement (1), wherein the cooling structure (9) is connected to the hollow shaft (2),
Hollow shaft arrangement (1), characterized in that the cooling structure (9) is part of a cooling body (8) formed separately from the hollow shaft (2).   2. The hollow shaft arrangement (1) according to claim 1, wherein the cooling body (8) is held in the inner space (3) in a press-fit manner, and in particular is clamped radially inside the inner space (3). . The outer diameter of the cooling body (8) _{(D 8)} is a bearing for mounting the hollow shaft (2) (13), greater than, especially two of the inner diameter of the bearing (13) _{(d 13),} according to claim 1 Or the hollow shaft arrangement (1) according to claim 2.   The outer peripheral surface (10) of the cooling body (8) is formed so as to complement the inner peripheral surface (12) of the hollow shaft (2). Hollow shaft arrangement (1). The outer peripheral surface (10) and the inner peripheral surface (12) are formed in a cylindrical shape in each case using an outer diameter (D ₈ ) and an inner diameter (d ₁₂ ) corresponding to each other. The hollow shaft arrangement (1) described in 1.   The hollow shaft arrangement (1) according to any of claims 1 to 5, wherein the cooling body (8) comprises a sleeve-like body (18) from which the cooling structure (9) projects radially inward.   The hollow shaft arrangement (1) according to claim 6, wherein the sleeve-like body (18) comprises a circumferential region (11) that can be reduced in the circumferential direction (U).   The hollow shaft arrangement (1) according to claim 6 or 7, wherein the sleeve-like body (18) comprises an axial gap (11).   Two ends (21) of the sleeve-like body (18) separated from each other by the axial gap (11) are connected to each other via an expansion fold (22) protruding radially inward. A hollow shaft arrangement (1) according to claim 7 or claim 8. The hollow shaft (2) is
It is a form consisting of multiple parts,
Including at least one receptacle portion (5) having an axial opening (15) for receiving the cooling body (8);
The hollow shaft arrangement (1) according to any of the preceding claims, comprising at least one closing portion (6, 7) for closing the axial opening (15). A method for assembling a hollow shaft arrangement (1) according to any of claims 1 to 10, comprising
Reducing the radial dimension of the cooling body (8) by a load of force acting radially inward;
Inserting the cooling body (8) into the internal space (3) through an axial opening (15) so as to shrink in the radial direction;
Removing the radial force load, so that the cooling body (8) increases radially and receives a press-fit connection to the hollow shaft (2);
Including methods. The cooling body installed state (8) has an outer diameter that is reduced at least 0.5% compared to the cooling of the non-installation state (D _8), The method of claim 11.

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